Marine environments, which include lakes, seas, oceans, streams, rivers and other bodies of water, present particular challenges to vessels traveling in such environments under the various illumination conditions and various visibility conditions. For example, various types of semi-submerged, or floating, obstacles and objects in marine environments, such as icebergs, whales, semi-submerged metal ship containers which have fallen overboard, large underwater rocks slightly protruding from the surface of the water, wood logs and the like, pose potential threats to ship hulls and ship propellers. This potential threat is increased under low illumination and bad visibility conditions, such as at night, during a storm or in heavy rain. In addition, the detection of objects in a marine environment, such as buoys or sea marks, as well as the detection of persons who have fallen overboard (i.e., ‘man overboard’), present a challenge for individuals on vessels attempting to locate such objects and persons due to the small surface area of these objects and persons appearing above the surface of the water. As above, the task of locating small objects and persons in a marine environment is made more difficult in low illumination and bad visibility conditions. Furthermore, small objects and persons are usually undetected by radar or thermal imagers (e.g., Near Infrared, Medium Infrared or Far infrared imagers). It is noted that the term ‘body of water’ herein refers to a body of water of sufficient size to support marine traffic. The term ‘object’ herein refers to semi-submerged, or floating, obstacles, objects or persons in a marine environment. Objects can include icebergs, whales, semi-submerged metal ship containers, large underwater rocks slightly protruding from the surface of the water at low tide, wood logs, buoys, persons and the like.
U.S. Pat. No. 6,693,561 to Kaplan, entitled “System for and method of wide searching for targets in a marine environment” is directed towards a system and a method of searching for targets, both animate and inanimate in a marine environment and comprises a transmitter means, a processor including a receiver means, and an indicator. The transmitter means is mounted on an object, which is above water, such as on-board a marine vessel, an aircraft, or on a seaside structure. The transmitter means emits first and second beams of optical radiation at first and second zones of water. The first beam has a first wavelength characteristic having wavelengths in the ultraviolet to blue range (300-475 nanometers), and capable of entering the first zone of water and being refracted there through as a refracted beam. The second beam has a second wavelength characteristic having wavelengths in the infrared range (650-1500 nanometers) and capable of reflecting from the second zone of water as a reflected beam. The processor is operative for identifying locations of the targets in the marine environment. The receiver means is operative for separately detecting return target reflections reflected off any targets impinged by the refracted and/or the reflected beams to find an identified target.
The indicator is operative for indicating the identified target. If the only target reflection detected is from the refracted beam, then an underwater target is identified. If the only target reflection detected is from the reflected beam, then an above water target is identified. If target reflections from both the refracted beam and the reflected beam are detected, then multiple targets are identified, or a single target extending both above and below the water is identified. The ultraviolet and infrared beams are pulsed, and the time width of each pulse and the spacing between pulses are known. By determining the time duration from the moment a transmitted pulse is emitted until a corresponding received pulse is detected, the distance or range to a target can be computed, as well as the depth to an underwater target. In addition, a deviation prism is located in front of the transceiver and is rotated to expand the target search area. An outgoing light beam and/or incoming target reflections pass un-obstructively through a central aperture of the prism so as to enable a forward search area along an axis to be continuously scanned. The beam and/or reflections are deviated by outer wedge-shaped portions of the prism to direct deviated light to one side or the other of the axis.
U.S. Pat. No. 7,379,164 to Inbar et al., entitled “Laser gated camera imaging system and method” is directed towards a gated camera imaging system and method, utilizing a laser device for generating a beam of long duration laser pulses toward a target. A camera receives the energy of light reflexes of the pulses reflected from the target. The camera gating is synchronized to be set ‘OFF’ for at least the duration of time it takes the laser device to produce a laser pulse in its substantial entirety, including an end of the laser pulse, in addition to the time it takes the laser pulse to complete traversing a zone proximate to the system and back to the camera. The camera gating is then set ‘ON’ for an ‘ON’ time duration thereafter, until the laser pulse reflects back from the target and is received in the camera.
The laser pulse width substantially corresponds to at least the ‘ON’ time duration. Preferably, the laser device includes a Diode Laser Array (DLA).
The system further includes an optical fiber for transferring the laser beam from the laser device to an optical fiber exit of the optical fiber, as well as gimbals, comprising a gyro feedback, for stabilizing the camera and the optical fiber exit of the optical fiber in a packaged module. The system also includes an image-process stabilizer and a support unit for supporting and providing height and rotational adjustments to the camera and the optical fiber exit of the optical fiber. The system also includes at least one filter for spectral and spatial filtering as well as an optical multiplier for enlarging the image of the target. The optical axis of the laser device can also be substantially parallel to the optical axis of the camera. The DLA can be implemented in the near IR range or the blue-green range of the visible light spectrum. The camera can include a Charge Coupled Device (CCD), a Gated Intensified Charge Injection Device (GICID), a Gated Intensified CCD (GICCD), a Gated Image Intensifier, or a Gated Intensified Active Pixel Sensor (GIAPS).